An open silicon microcontroller with a Z80, MOS6502, and M68K - start the open silicon revolution

After a good start the campaign is going slower now. We are over half way and 17% of the funding goal is reached. It is time now to back this project if you want it to succeed.

In this update I will discuss how first time right was taken as target for the Retro-uC project from the start; the details on the QFP package of the Retro-uC chip and the

First time right

A second source of comments on the Retro-uC campaign was about the fact the project assumes the chip will work the first time; in the industry also known as first-time-right. This goal has been taken into account during the definition of the Retro-uC project from the start. It was performed by applying the KISS principle at several levels of the project:

re-use of well tested (open source) RTL as much as possible to avoid having bugs

don’t use analog blocks on the chips; they typically need one or more iterations to get right

avoid feature creep by introducing lots of features that may also introduce bugs

use of mature technology node; this reduces complexity of the chip and the maximum speed. This in itself will make is possible to have the timing, power distribution and signal integrity right from the first time.

QFP package

The package for the Retro-uC chip has been finalized. It will be a 100-pin QFP package of 14mm x 20mm. The details can be seen in the next picture:

You can see that this package is rectangular and has a 0.65mm pitch of the pins. A square version with a higher pin pitch was not available as open tool. Making a custom package would need more than $10 000 extra for the tooling start-up costs.

Also a preliminary pin list is given in the next table:

Pin

Net

1

VCORE

2

GND

3

GND

4

VIO

5-26

PA1-PA22

27

VIO

28

GND

29

GND

30

VCORE

31-50

PB1-PB20

51

VCORE

52

GND

53

GND

54

VIO

55-76

PC1-PC22

77

VIO

78

GND

79

GND

80

VCORE

81-89

PD1-PD9

90

TDI

91

TDO

92

TCK

93

TMS

94

TRST_N

95

RESET_N

96

CLK

97

I2CBOOT

98

ENM68K

99

ENZ80

100

EN6502

VCORE is the supply for the logic on the chip and has to be 3.3V; VIO can be chosen to be 3.3V or 5V to have 3.3V or 5V I/O. It still need to be finalized how the input and outputs of the peripherals are shared with the I/O pins on the chip. An update of the pin list will be given when this is done.

Development test material

In order to test the peripherals on the Retro-uC I ordered some chips to allow testing the implementation on an FPGA. You can see the chips I got in the next picture:

These chips are meant to test the I2C boot feature of the Retro-uC and also for investigating the possibility of providing a SRAM interface on the pins of the Retro-uC. When successful it allows to have external memory extra to the 4 kB on chip memory or usable for other memory mapped access to external devices. This is a feature often requested that should allow to use the Retro-uC also as a microprocessor and not only as a microcontroller. I do think this feature should be able to be implemented without risk of messing up the rest of the chip so I am willing to make a compromise on the minimal number of features strategy to reach first time right for the Retro-uC. In one of the next updates it will be announced if this feature will be added to the Retro-uC.

Support Chips4Makers!

Thanks for supporting to get the open silicon movement started. You will be remembered until eternity!

$42

Retro-uC Chip

The Retro-uC chip in a QFP package.

Orders placed now ship Mar 15, 2019.

Free US Shipping / $8 Worldwide

$89

Retrino

The Retro-uC on a board with Arduino Mega footprint and compatible I/O. USB is used to power the board and for programming it.

Orders placed now ship Apr 20, 2019.

Free US Shipping / $10 Worldwide

$59

Retro-uC Breadboard

A Retro-uC mounted on a PCB that is breadboardable. The board is delivered with headers that make the board compatible with classic DIL chips. The headers are not mounted yet and need to be soldered manually.

Orders placed now ship Apr 20, 2019.

Free US Shipping / $10 Worldwide

$65

Retro-uC ProtoPlus

The Retro-uC mounted on a Perf2+ style prototype board.

Orders placed now ship Apr 20, 2019.

Free US Shipping / $5 Worldwide

$280

Retro-uC Fired Up Pack

A pack for the Retro-uC and open silicon believer to show their support. The pack contains the Retro-uC chip and one of each Retro-uC board. It will also give early access to the Chips4Makers developer board that will be set up after the Retro-uC chip has been taped out.

Orders placed now ship Apr 20, 2019.

Free Worldwide Shipping

$420

Retro-uC Chip Developer Pack

The Fired Up Pack with an additional Digilent FPGA board pre-loaded with Retro-uC source code and delivered early so you can start developing your own IC. The FPGA will be shipped the same time when the development hub will be opened, the Retro-uC Fired Up Pack will be shipped later.